1095: Prenatal diagnosis during the first trimester

Abstract

Ultrasound measurement of nuchal translucency thickness is an effective method of screening for chromosomal abnormalities at 11 to 13 + 6 wk of gestation. It was suggested that, when combined with maternal age, this method can identify about 80% of pregnancies with trisomy 21 at a 5% false-positive rate. It was shown that by the combination of this methodology with the determination of maternal serum free-human chorionic gonadotropin (-hCG) and pregnancy-associated plasma protein-A (PAPP-A), the detection rate of trisomy 21 is about 90%, for a false-positive rate of 5%. Additionally, in chromosomally normal fetuses, increased NT is associated with an increased risk of structural abnormalities, mainly cardiac defects, genetic syndromes and adverse pregnancy outcome. It was also reported that there is an association between chromosomal defects and abnormal ductus venosus blood flow-velocity waveforms (DV-FVWs) at 11 to14 wk of gestation in high-risk pregnancies. More than that, an abnormal DV-FVW is also associated with a high probability of an underlying major cardiac defect, and adverse pregnancy outcome. It was also proposed that a high association between absent fetal nasal bone at the 11 to 13 + 6 gestational wk scan and trisomy so that the addition of this marker could result in a major reduction in the need for invasive testing and a substantial increase in sensitivity. During this lecture, we will review the ultrasound technique for obtaining these different markers correctly according to the Fetal Medicine Foundation criteria. Additionally, we will discuss our experience in two private centers in Argentina during the last 4y. Ultrasound measurement of nuchal translucency thickness is an effective method of screening for chromosomal abnormalities at 11 to 13 + 6 wk of gestation. It was suggested that, when combined with maternal age, this method can identify about 80% of pregnancies with trisomy 21 at a 5% false-positive rate. It was shown that by the combination of this methodology with the determination of maternal serum free-human chorionic gonadotropin (-hCG) and pregnancy-associated plasma protein-A (PAPP-A), the detection rate of trisomy 21 is about 90%, for a false-positive rate of 5%. Additionally, in chromosomally normal fetuses, increased NT is associated with an increased risk of structural abnormalities, mainly cardiac defects, genetic syndromes and adverse pregnancy outcome. It was also reported that there is an association between chromosomal defects and abnormal ductus venosus blood flow-velocity waveforms (DV-FVWs) at 11 to14 wk of gestation in high-risk pregnancies. More than that, an abnormal DV-FVW is also associated with a high probability of an underlying major cardiac defect, and adverse pregnancy outcome. It was also proposed that a high association between absent fetal nasal bone at the 11 to 13 + 6 gestational wk scan and trisomy so that the addition of this marker could result in a major reduction in the need for invasive testing and a substantial increase in sensitivity. During this lecture, we will review the ultrasound technique for obtaining these different markers correctly according to the Fetal Medicine Foundation criteria. Additionally, we will discuss our experience in two private centers in Argentina during the last 4y.